[PATCH v4 5/7] ARM: NOMMU: Introduce dma operations for noMMU
Vladimir Murzin
vladimir.murzin at arm.com
Mon Apr 24 06:16:55 EDT 2017
R/M classes of cpus can have memory covered by MPU which in turn might
configure RAM as Normal i.e. bufferable and cacheable. It breaks
dma_alloc_coherent() and friends, since data can stuck in caches now
or be buffered.
This patch factors out DMA support for NOMMU configuration into
separate entity which provides dedicated dma_ops. We have to handle
there several cases:
- configurations with MMU/MPU setup
- configurations without MMU/MPU setup
- special case for M-class, since caches and MPU there are optional
In general we rely on default DMA area for coherent allocations or/and
per-device memory reserves suitable for coherent DMA, so if such
regions are set coherent allocations go from there.
In case MMU/MPU was not setup we fallback to normal page allocator for
DMA memory allocation.
In case we run M-class cpus, for configuration without cache support
(like Cortex-M3/M4) dma operations are forced to be coherent and wired
with dma-noop (such decision is made based on cacheid global
variable); however, if caches are detected there and no DMA coherent
region is given (either default or per-device), dma is disallowed even
MPU is not set - it is because M-class implement system memory map
which defines part of address space as Normal memory.
Reported-by: Alexandre Torgue <alexandre.torgue at st.com>
Reported-by: Andras Szemzo <sza at esh.hu>
Tested-by: Benjamin Gaignard <benjamin.gaignard at linaro.org>
Tested-by: Andras Szemzo <sza at esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue at st.com>
Reviewed-by: Robin Murphy <robin.murphy at arm.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>
Acked-by: Arnd Bergmann <arnd at arndb.de>
---
arch/arm/Kconfig | 1 +
arch/arm/include/asm/dma-mapping.h | 2 +-
arch/arm/mm/Makefile | 5 +-
arch/arm/mm/dma-mapping-nommu.c | 253 +++++++++++++++++++++++++++++++++++++
4 files changed, 257 insertions(+), 4 deletions(-)
create mode 100644 arch/arm/mm/dma-mapping-nommu.c
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 6ab63fa..8f0b6ca 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -22,6 +22,7 @@ config ARM
select CLONE_BACKWARDS
select CPU_PM if (SUSPEND || CPU_IDLE)
select DCACHE_WORD_ACCESS if HAVE_EFFICIENT_UNALIGNED_ACCESS
+ select DMA_NOOP_OPS if !MMU
select EDAC_SUPPORT
select EDAC_ATOMIC_SCRUB
select GENERIC_ALLOCATOR
diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
index 7166569..63270de 100644
--- a/arch/arm/include/asm/dma-mapping.h
+++ b/arch/arm/include/asm/dma-mapping.h
@@ -20,7 +20,7 @@ static inline const struct dma_map_ops *__generic_dma_ops(struct device *dev)
{
if (dev && dev->dma_ops)
return dev->dma_ops;
- return &arm_dma_ops;
+ return IS_ENABLED(CONFIG_MMU) ? &arm_dma_ops : &dma_noop_ops;
}
static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
diff --git a/arch/arm/mm/Makefile b/arch/arm/mm/Makefile
index 54857bc..ea80df7 100644
--- a/arch/arm/mm/Makefile
+++ b/arch/arm/mm/Makefile
@@ -2,9 +2,8 @@
# Makefile for the linux arm-specific parts of the memory manager.
#
-obj-y := dma-mapping.o extable.o fault.o init.o \
- iomap.o
-
+obj-y := extable.o fault.o init.o iomap.o
+obj-y += dma-mapping$(MMUEXT).o
obj-$(CONFIG_MMU) += fault-armv.o flush.o idmap.o ioremap.o \
mmap.o pgd.o mmu.o pageattr.o
diff --git a/arch/arm/mm/dma-mapping-nommu.c b/arch/arm/mm/dma-mapping-nommu.c
new file mode 100644
index 0000000..3ba3003
--- /dev/null
+++ b/arch/arm/mm/dma-mapping-nommu.c
@@ -0,0 +1,253 @@
+/*
+ * Based on linux/arch/arm/mm/dma-mapping.c
+ *
+ * Copyright (C) 2000-2004 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/dma-mapping.h>
+#include <linux/scatterlist.h>
+
+#include <asm/cachetype.h>
+#include <asm/cacheflush.h>
+#include <asm/outercache.h>
+#include <asm/cp15.h>
+
+#include "dma.h"
+
+/*
+ * dma_noop_ops is used if
+ * - MMU/MPU is off
+ * - cpu is v7m w/o cache support
+ * - device is coherent
+ * otherwise arm_nommu_dma_ops is used.
+ *
+ * arm_nommu_dma_ops rely on consistent DMA memory (please, refer to
+ * [1] on how to declare such memory).
+ *
+ * [1] Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
+ */
+
+static void *arm_nommu_dma_alloc(struct device *dev, size_t size,
+ dma_addr_t *dma_handle, gfp_t gfp,
+ unsigned long attrs)
+
+{
+ const struct dma_map_ops *ops = &dma_noop_ops;
+
+ /*
+ * We are here because:
+ * - no consistent DMA region has been defined, so we can't
+ * continue.
+ * - there is no space left in consistent DMA region, so we
+ * only can fallback to generic allocator if we are
+ * advertised that consistency is not required.
+ */
+
+ if (attrs & DMA_ATTR_NON_CONSISTENT)
+ return ops->alloc(dev, size, dma_handle, gfp, attrs);
+
+ WARN_ON_ONCE(1);
+ return NULL;
+}
+
+static void arm_nommu_dma_free(struct device *dev, size_t size,
+ void *cpu_addr, dma_addr_t dma_addr,
+ unsigned long attrs)
+{
+ const struct dma_map_ops *ops = &dma_noop_ops;
+
+ if (attrs & DMA_ATTR_NON_CONSISTENT)
+ ops->free(dev, size, cpu_addr, dma_addr, attrs);
+ else
+ WARN_ON_ONCE(1);
+
+ return;
+}
+
+static int arm_nommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
+ void *cpu_addr, dma_addr_t dma_addr, size_t size,
+ unsigned long attrs)
+{
+ const struct dma_map_ops *ops = &dma_noop_ops;
+ int ret;
+
+ if (dma_mmap_from_coherent(dev, vma, cpu_addr, size, &ret))
+ return ret;
+
+ if (attrs & DMA_ATTR_NON_CONSISTENT)
+ return ops->mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
+
+ WARN_ON_ONCE(1);
+ return -ENXIO;
+}
+
+static void __dma_page_cpu_to_dev(phys_addr_t paddr, size_t size,
+ enum dma_data_direction dir)
+{
+ dmac_map_area(__va(paddr), size, dir);
+
+ if (dir == DMA_FROM_DEVICE)
+ outer_inv_range(paddr, paddr + size);
+ else
+ outer_clean_range(paddr, paddr + size);
+}
+
+static void __dma_page_dev_to_cpu(phys_addr_t paddr, size_t size,
+ enum dma_data_direction dir)
+{
+ if (dir != DMA_TO_DEVICE) {
+ outer_inv_range(paddr, paddr + size);
+ dmac_unmap_area(__va(paddr), size, dir);
+ }
+}
+
+static dma_addr_t arm_nommu_dma_map_page(struct device *dev, struct page *page,
+ unsigned long offset, size_t size,
+ enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ dma_addr_t handle = page_to_phys(page) + offset;
+
+ __dma_page_cpu_to_dev(handle, size, dir);
+
+ return handle;
+}
+
+static void arm_nommu_dma_unmap_page(struct device *dev, dma_addr_t handle,
+ size_t size, enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ __dma_page_dev_to_cpu(handle, size, dir);
+}
+
+
+static int arm_nommu_dma_map_sg(struct device *dev, struct scatterlist *sgl,
+ int nents, enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ int i;
+ struct scatterlist *sg;
+
+ for_each_sg(sgl, sg, nents, i) {
+ sg_dma_address(sg) = sg_phys(sg);
+ sg_dma_len(sg) = sg->length;
+ __dma_page_cpu_to_dev(sg_dma_address(sg), sg_dma_len(sg), dir);
+ }
+
+ return nents;
+}
+
+static void arm_nommu_dma_unmap_sg(struct device *dev, struct scatterlist *sgl,
+ int nents, enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ struct scatterlist *sg;
+ int i;
+
+ for_each_sg(sgl, sg, nents, i)
+ __dma_page_dev_to_cpu(sg_dma_address(sg), sg_dma_len(sg), dir);
+}
+
+static void arm_nommu_dma_sync_single_for_device(struct device *dev,
+ dma_addr_t handle, size_t size, enum dma_data_direction dir)
+{
+ __dma_page_cpu_to_dev(handle, size, dir);
+}
+
+static void arm_nommu_dma_sync_single_for_cpu(struct device *dev,
+ dma_addr_t handle, size_t size, enum dma_data_direction dir)
+{
+ __dma_page_cpu_to_dev(handle, size, dir);
+}
+
+static void arm_nommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
+ int nents, enum dma_data_direction dir)
+{
+ struct scatterlist *sg;
+ int i;
+
+ for_each_sg(sgl, sg, nents, i)
+ __dma_page_cpu_to_dev(sg_dma_address(sg), sg_dma_len(sg), dir);
+}
+
+static void arm_nommu_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
+ int nents, enum dma_data_direction dir)
+{
+ struct scatterlist *sg;
+ int i;
+
+ for_each_sg(sgl, sg, nents, i)
+ __dma_page_dev_to_cpu(sg_dma_address(sg), sg_dma_len(sg), dir);
+}
+
+const struct dma_map_ops arm_nommu_dma_ops = {
+ .alloc = arm_nommu_dma_alloc,
+ .free = arm_nommu_dma_free,
+ .mmap = arm_nommu_dma_mmap,
+ .map_page = arm_nommu_dma_map_page,
+ .unmap_page = arm_nommu_dma_unmap_page,
+ .map_sg = arm_nommu_dma_map_sg,
+ .unmap_sg = arm_nommu_dma_unmap_sg,
+ .sync_single_for_device = arm_nommu_dma_sync_single_for_device,
+ .sync_single_for_cpu = arm_nommu_dma_sync_single_for_cpu,
+ .sync_sg_for_device = arm_nommu_dma_sync_sg_for_device,
+ .sync_sg_for_cpu = arm_nommu_dma_sync_sg_for_cpu,
+};
+EXPORT_SYMBOL(arm_nommu_dma_ops);
+
+static const struct dma_map_ops *arm_nommu_get_dma_map_ops(bool coherent)
+{
+ return coherent ? &dma_noop_ops : &arm_nommu_dma_ops;
+}
+
+void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
+ const struct iommu_ops *iommu, bool coherent)
+{
+ const struct dma_map_ops *dma_ops;
+
+ if (IS_ENABLED(CONFIG_CPU_V7M)) {
+ /*
+ * Cache support for v7m is optional, so can be treated as
+ * coherent if no cache has been detected. Note that it is not
+ * enough to check if MPU is in use or not since in absense of
+ * MPU system memory map is used.
+ */
+ dev->archdata.dma_coherent = (cacheid) ? coherent : true;
+ } else {
+ /*
+ * Assume coherent DMA in case MMU/MPU has not been set up.
+ */
+ dev->archdata.dma_coherent = (get_cr() & CR_M) ? coherent : true;
+ }
+
+ dma_ops = arm_nommu_get_dma_map_ops(dev->archdata.dma_coherent);
+
+ set_dma_ops(dev, dma_ops);
+}
+
+void arch_teardown_dma_ops(struct device *dev)
+{
+}
+
+int dma_supported(struct device *dev, u64 mask)
+{
+ return 1;
+}
+
+EXPORT_SYMBOL(dma_supported);
+
+#define PREALLOC_DMA_DEBUG_ENTRIES 4096
+
+static int __init dma_debug_do_init(void)
+{
+ dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);
+ return 0;
+}
+core_initcall(dma_debug_do_init);
--
2.0.0
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